Page 165 - The Green Building Bottom Line The Real Cost of Sustainable Building

144 CHAPTER 5

emissions of heat-trapping greenhouse gases. Strategies that reduce the heat island
effect can reduce the power plant emissions that contribute to global warming.
The south side of Savannah, where Abercorn Common is located, is typically four
to five degrees warmer in the summer months than other areas of the city, a difference
I could always feel as I drove back and forth from our office in downtown Savannah,
with its thick tree canopy, to the south side of Savannah each day during the two years
Abercorn Common was under construction. There are three ways to mitigate the heat
island effect: through choice of roofing material, with plants, and with reflective
paving surfaces. At Abercorn Common, we used all three measures.
As part of our plan to combat the heat island effect, we specified that each roof on
our buildings be covered with a high-albedo white thermoplastic polyolefin (TPO)
membrane, which reflects heat and allows our roof surfaces to be 20 to 30 degrees
cooler in the dead of summer. (Albedo is a measure of a material’s solar reflectance,
its ability to reflect sunlight.) TPO products aren’t more expensive; in fact, they actu-
ally cost less than traditional built-up roof membranes. In addition, TPO material can
be recycled and reprocessed. The combination of the highly reflective, high-albedo
roof surfaces and the tree canopy provided by the oak and palm trees means more than
30 percent of the site is reflective and shaded. See Figure 5.2 for an aerial view.

DE-ENERGIZING THE EXTERIOR LOOK
The exterior facades of Abercorn Common—some brick, some stucco, like old Savan-
nah—look substantial and beefy and are built to last. In our negotiations with tenants

Figure 5.2 Aerial photo of the Abercorn Common site.